Improvement in meridian-instruments



F. YEISER.

Altitude Instrument.

Patented Dec. 17, 1861.

UNrrED STATES PATENT @FFICE.

FREDERICK YEISER, OF DANVI'LLE, KENTUCKY.

IMPROVEMENT IN MERIDIAN-INSTRUMENTS.

Specification forming part of Letters Patent No. 33,970, dated December 17, 1861.

T0 (ZZZ whom it may concern: I

Be it known that I, FREDERICK YEISER, of Danville, in the county of Boyle and State of Kentucky, have invented a new and useful Instrument for Determining the True Meridian; and I do hereby declare that the'following is a full, clear, and exact description of the same, reference being had to the annexed drawings, making a part of this specification, in which Figures 1 and 2 are side views of my instrument. Fig. 3 is a top view, and Fig. 4 is a perspective view of the same.

Similar letters of reference in the several figures indicate corresponding parts.

This invention consists in certain means hereinafter described for determining the plane of the meridian and apparent noon.

To enable others to make and use my instrument, I will proceed to describe the construction and operation of the same.

It should be made of metal'or other suitable material.

A is the base-plate of the instrument.

B is a pillar or cylinder, one end of which goes through and is fastened in a hole in the center of the base-plate A. The other end of said pillar is similarly fastened to the disk 0. Being thus connected by the pillar B, the plate A and disk 0 are precisely parallel one to the other. On the opposite side of the disk 0 from that which is fastened to the, end of the pillar Bis attached the moving part of the instrument, which consists of the bars D and G. The bar D is attached to the disk 0 by a pivot or shaft, one end of which is fastened in the center of the disk 0, and the other portion projects above the face of the disk and passes through the middle of the bar D, allowing said bar to move or rotate freely around it and precisely parallel to the disk G. The bevel E on one side of the bar D, is for the purpose of allowing a sharp-pointed markinginstrument to move close to the edge or side of the bar D when a line is drawn with said instrument on the disk 0, which will be hereinafter more fully described. The bar G is attached to the endof the bar Dbya shaft or pivot passing through the middle, or near to it, of the bar G and fastened into the end of the bar D. Said bar G moves freely on said shaft or pivot and precisely at right angles to the movement of the bar D, it being attached to the end of said bar precisely at right angles to it. The bar G has fastened to each end a small square plate J and J, standing out at right anglesfrorn it. Through the'plate J is an opening or small hole for the purpose of receiving a small convex lens. On the opposite plate J are two sets of parallel lines, drawn crossing each other at right angles at a suitable distance apart to embrace the suns image, which falls between them from the lens. In order to distinguish the two said sets of lines from each other, I- will call one set equatorial lines and the other set hour lines. The set which is parallel to the disk Owhen the bar G is brought to a horizontal position are the equatorial lines, and the other set crossing them at right angles are the hour-lines. I have called them equatorialand hour lines from the fact that after the meridian is obtained, when an observation is taken with the instrument to ascertain the hour of twelve oclock, or noon, the said equatorial lines will be parallel with the equatorial plane and the suns image will only fall between the said hour-lines, which cross the said equatorial lines at right angles at the hour of twelve oclock, or noon.

F is an are or quadrant fastened to the end of the bar D and parallel to the bar G, so arranged thathaving an arched slot and a clampscrew the lens-bar G can be held firmly at any angle desired from a horizontal to a vertical position. The said are or quadrant F is not an essential part of the instrument, for if the bar G fits on the shaft or pivot that attaches it to the end of the bar I) with sufficient tenseness for said bar G to remain at any angle it is placed, it renders the quadrant an unnecessary appendage. When the instrument is brought to a level, the baseplate A and disk G are horizontal. The bar D rotates horizontally and carries the bar G with it. G has a rotary movement in a ver tical plane.

The operation of the instrument is as fol lows: The instrument is leveled by the usual modes of leveling. An observation is taken in the forenoon by adjusting the lens-bar G until the suns image falls from the lens pre cisely in the small square formed by the hour and equatorial lines crossing each other in the center of the plate J. A line is then drawn on the disk 0 close to the beveled edge of the bar D without altering the angle of the lensbar G from its adjustment for the observation taken,as described. A short time before the corresponding time in the afternoon turn the bar D horizontally, which carries the lens-bar G with it in the direction the sun travels until the lens in the plate J is opposite the sun and its image falls from the lens between the hour-lines on the plate J. Keep the suns image between the hour-lines by turning the bar D horizontally, as the suns image moves, until it is in the small square in the center of the plate J. Atthat moment cease moving the bar D and draw a line on the disk 0 close to the beveled edge of the bar D. Now draw a line precisely half-way between the two lines marked on the disk 0, as described. Now if the beveled edge of the bar D is on the bisecting line the lensbar G is in a position (by adjusting it in the vertical plane in which it rotates) to take an altitude of the sun precisely half-way between the altitudes taken as described. The said bisecting altitude would be its highest altitude, which is noon. Therefore at noon any day after, if the sun is not obscured and the lens-bar G is adjusted in the vertical plane in which it rotates so the lens will be opposite, or nearly so, to the sun, the suns image will fall from the lens onto the plate J and between the hour-lines on said plate, and if the lens-bar G were brought to a vertical position the hour-lines on the plate J would be parallel with the plane of the meridian, and were a line marked across the said plate precisely dividing the space between and parallel with the hour-lines on said plate J the vertical plane passing through said line would be the plane of the meridian.

What I claim as my invention, and desire to secure by Letters Patent, is-

In combination with the bar G and plates J J, the bar D and disk 0, operated substantially in the manner and for the purposes set forth.

F. YEISER.

Witnesses:

JAMES G. MCAFEE, SPEED S. FRY. 

